Image sensors are widely used in various imaging applications and products, such as cameras, scanners, photocopiers, etc. A performance of an image sensor is depended on quality of pixels in the image sensors. As a part of IC evolution for semiconductor image sensors, the size of pixels has been steadily reduced. As the size of pixels continue to shrink, quality of pixels become more difficult to control.
The quality of pixels can affect performance such as an amount of dark current. The dark current is one of sources for noise in the image sensors. The dark current is referred to as a leakage current in non-optical devices such as in transistors.